An inverted river, called Daotanghe in Chinese, refers to a river that originates in the Qagan prairie at the piedmont of Riyue (Sun and Moon) Mountain and flows from east to west into Qinghai Lake. This river is at an elevation of 3,300 m and is 40 km long. Daotanghe originally flowed east into Huanghe (Yellow River) with the Buha River and Luohantang River. After the uplift of Riyue Mountain due to tectonic movements, the river changed direction to become an inverted river that flows west into Qinghai Lake. It is the smallest portion of the Qinghai Lake system. At high tide, water from Qinghai Lake flows back into the river, which is another reason that this river was given its name.